In a bowl combine gram flour, salt, sugar and asafoetida. Add oil, green chilli, ginger and make a batter using some batter. (Batter should be of a pouring consistency.)
Add fruit salt.(The batter will ferment instantly.)
Grease a steel pan or a tray using some oil and pour in the batter.
Batter should be filled up to half of the pan or tray.
Heat water in an Idli steamer and place this pan or tray filled with batter and steamed covered for 20-25 minutes.
When cooked, remove from steamer and take out from pan or tray. Keep aside.
To make a tempering-
Heat oil in a pan and add mustard, green chillies and curry leaves. Add vinegar and sufficient water to soak the khaman.
Pour this mixture over the steamed khaman and let it cool down.
When cold, cut into pieces of desired size and serve garnished with chopped coriander and grated coconut.